The present invention relates to a novel type of method of producing substituted 2-nitroguanidine derivatives.
It is known that, in order to produce 1,3-disubstituted 2-nitroguanidines, a further substituent may be introduced into monosubstituted 2-nitroguanidines (e.g. by alkylation) (see e.g. EP patent applications 0.375.907, 0.376.279 and 0.383.091). Owing to the presence of three reactive hydrogen atoms in the monosubstituted 2-nitroguanidines used as the starting material in these reactions, the previously proposed substitution reactions of this kind are often non-selective and lead to undesired substitution products. The mentioned EP patent applications describe the production of 1,3-disubstituted 2-nitroguanidines by reacting monosubstituted nitroisothioureas with primary amines whilst cleaving mercaptan. However, these nitroisothiourea compounds, containing alkylthio leaving groups, which are proposed as starting compounds in the known processes, can only be obtained with difficulty. In addition, in EP-A-0-483.062, a method of producing the compounds of formula (I) by hydrolysis of hexahydro-triazines is described.
It has now been shown that the above-described methods of producing compounds of formula (I) do not satisfy the requirements demanded of a chemical production process, such as availability, toxicity, stability in storage and purity of the starting materials and excipients, reaction time, energy consumption and volumes yielded by the process, quantity and recovery of the accruing by-products and waste products, as well as purity and yield of the end product. There is therefore a need to provide improved methods of producing these compounds. It has now surprisingly been found that the method according to the invention is able to satisfy these requirements to a large extent.
Accordingly, it is the aim of the present invention to provide an improved method of producing 1-monosubstituted and 1,3-disubstituted 2-nitroguanidines from readily obtainable starting compounds, which allows specific 1,3-disubstitution without obtaining major amounts of undesired by-products.
The object of the invention is
a) a method of producing a compound of formula 
xe2x80x83and, if appropriate, the E/Z isomers, E/Z isomeric mixtures and/or tautomers thereof, each in free form or in salt form, wherein
R1 is hydrogen or C1-C4-alkyl;
R2 is hydrogen, C1-C6-alkyl, C3-C6-cycloalkyl or a radical xe2x80x94CH2B;
Het is an aromatic or non-aromatic, monocyclic or bicyclic heterocyclic radical which is unsubstituted orxe2x80x94depending on the substitution possibilities of the ring systemxe2x80x94mono- to penta-substituted by substituents selected from the group comprising halogen, C1-C3-alkyl, C1-C3-alkoxy, halogen-C1-C3-alkyl, C1-C3-halogenalkoxy, cyclopropyl, halogencyclopropyl, C2-C3-alkenyl, C2-C3-alkynyl, C2-C3-halogenalkenyl and C2-C3-halogenalkynyl, C1-C3-alkylthio, C1-C3-halogenalkylthio, allyloxy, propargyloxy, allylthio, propargylthio, halogenallyloxy, halogenallylthio, cyano and nitro; and
B is phenyl, 3-pyridyl or thiazolyl, which are optionally substituted by one to three substituents from the group comprising C1-C3-alkyl, C1-C3-halogenalkyl, cyclopropyl, halogencyclopropyl, C2-C3-alkenyl, C2-C3-alkynyl, C1-C3-alkoxy, C2-C3-halogenalkenyl, C2-C3-halogenalkynyl, C1-C3-halogenalkoxy, C1-C3-alkylthio, C1-C3-halogenalkylthio, allyloxy, propargyloxy, allylthio, propargylthio, halogenallyloxy, halogenallylthio, halogen, cyano and nitro;
xe2x80x83characterised by hydrolysing a compound of formula
Qxe2x80x94Axe2x80x94Qxe2x80x83xe2x80x83(IIa),
wherein A is a direct bond or an organic radical; or of formula 
wherein U is an organic radical; and in compounds (IIa) and (IIb) Q signifies 
and R1, R2 and Het are as defined above for formula (I), and optionally the E/Z isomers, E/Z isomeric mixtures and/or tautomers thereof, each in free form or in salt form.
The compounds of formula (I) may be present as E/Z isomers, e.g. in the following two isomeric forms 
Accordingly, any reference to compounds of formula (I) hereinbefore and hereinafter is understood to include also their corresponding E/Z isomers, even if the latter are not specifically mentioned in each case.
The compounds of formula (I) may be present partly in the form of tautomers. Accordingly, any reference to compounds of formula (I) hereinbefore and hereinafter is understood to include also their corresponding tautomers, even if the latter are not specifically mentioned in each case.
The compounds of formula (I) and, where appropriate, the E/Z isomers and tautomers thereof, may be present as salts. Compounds of formula (I) having at least one basic centre may form e.g. acid addition salts. These are formed for example with strong inorganic acids, such as mineral acids, e.g. sulfuric acid, a phosphoric acid or a hydrohalic acid, or with strong organic carboxylic acids, such as C1-C4alkanecarboxylic acids substituted where appropriate for example by halogen, e.g. acetic acid, such as optionally unsaturated dicarboxylic acids, e.g. oxalic, malonic, maleic, fumaric or phthalic acid, such as hydroxycarboxylic acids, e.g. ascorbic, lactic, malic, tartaric or citric acid, or benzoic acid, or with organic sulfonic acids, typically C1-C4alkane or arylsulfonic acids substituted where appropriate for example by halogen, e.g. methane-, trifluoromethane- or p-toluene-sulfonic acid. Salts of compounds of formula (I) with acids of the said kind are preferably obtained when working up the reaction mixtures.
In a broader sense, compounds of formula (I) with at least one acid group can form salts with bases. Suitable salts with bases are for example metal salts, typically alkali or alkaline earth metal salts, e.g. sodium, potassium or magnesium salts, or salts with ammonia or an organic amine, such as morpholine, piperidine, pyrrolidine, a mono-, di- or tri-lower alkylamine, e.g. ethyl-, diethyl-, triethyl- or dimethylpropylamine, or a mono-, di- or trihydroxy-lower alkylamine, e.g. mono-, di- or triethanolamine. Corresponding internal salts where appropriate may also be formed. Preferred compounds within the scope of this invention are agrochemically advantageous salts. Hereinbefore and hereinafter, the free compounds of formula (I) are understood where appropriate to include also by analogy the corresponding salts, or the salts are understood to include also the free compounds of formula (I). The same applies to E/Z isomers and tautomers of compounds of formula (I) and salts thereof. The free form is preferred.
The statements made about the free compounds of formula (I) or the E/Z isomers and tautomers and salts thereof also apply by analogy to the compounds of formulae (IIa) and (IIb), as well as the compounds of formulae (IIIa) and (IIIb) below.
In the definitions of the above formulae (I), (IIa), (IIb) and of the compounds of formulae (IIIa) and (IIIb) below, the individual generic terms are to be understood as follows:
The halogen atoms considered as substituents may be both fluorine and chlorine, and bromine and iodine, whereby fluorine, chlorine and bromine are preferred, especially chlorine. Halogen in this context is understood to be an independent substituent or part of a substituent, such as in halogenalkyl, halogenalkylthio, halogenalkoxy, halogencycloalkyl, halogenalkenyl, halogenalkynyl, halogenallyloxy or halogenallylthio. The alkyl, alkylthio, alkenyl, alkynyl and alkoxy radicals considered as substituents may be straight-chained or branched. Examples of such alkyls which may be mentioned are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec.-butyl or tert.-butyl. Suitable alkoxy radicals which may be mentioned are, inter alia: methoxy, ethoxy, propoxy, isopropoxy or butoxy and the isomers thereof. Alkylthio is for example methylthio, ethylthio, isopropylthio, propylthio or the isomeric butylthio. If the alkyl, alkoxy, alkenyl, alkynyl or cycloalkyl groups considered as substituents are substituted by halogen, they may be only partially halogenated or also perhalogenated. The above-mentioned definitions apply here to halogen, alkyl and alkoxy. Examples of the alkyl elements of these groups are methyl which is mono- to trisubstituted by fluorine, chlorine and/or bromine, such as CHF2 or CF3; ethyl which is mono- to pentasubstituted by fluorine, chlorine and/or bromine, such as CH2CF3, CF2CF3, CF2CCl3, CF2CHCl2, CF2CHF2, CF2CFCl2, CF2CHBr2, CF2CHClF, CF2CHBrF or CClFCHClF; propyl or isopropyl, mono- to heptasubstituted by fluorine, chlorine and/or bromine, such as CH2CHBrCH2Br, CF2CHFCF3, CH2CF2CF3 or CH(CF3)2; butyl or one of its isomers, mono- to nonasubstituted by fluorine, chlorine and/or bromine, such as CF(CF3)CHFCF3 or CH2(CF2)2CF3; 2-chlorocyclopropyl or 2,2-difluorocyclopropyl; 2,2-difluorovinyl, 2,2-dichlorovinyl, 2-chloroalkyl, 2,3-dichlorovinyl or 2,3-dibromovinyl.
If the defined alkyl, alkoxy or cycloalkyl groups are substituted by other substituents, they may be mono- or repeatedly substituted by identical or different substituents from those listed. In the substituted groups, it is preferable for one or two further substituents to be present. The cycloalkyl radicals considered as substituents may be, for example, cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. Alkenyl and alkynyl groups contain an unsaturated carbon-carbon bond. Typical representatives are allyl, methallyl or propargyl, but also vinyl and ethynyl. The double or triple bonds in allyloxy, propargyloxy, allylthio or propargylthio are separated from the connection point to the hetero atom (O or S) preferably by a saturated carbon atom.
As with the above-mentioned alkyl, alkenyl and alkynyl groups, the alkylene, alkenylene and alkynylene groups defined in the following may also be straight-chained or branched. Examples are xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94C(CH3)Hxe2x80x94 and xe2x80x94C(CH3)Hxe2x80x94C(CH3)Hxe2x80x94. The alkylene, alkenylene, alkynylene, cycloalkylene, arylene or heterocyclyl groups listed below are, where appropriate, substituted in the same way as the above-mentioned alkyl, alkenyl and alkynyl groups.
Aryl or arylene signifies phenyl or naphthyl, or phenylene or naphthylene, especially phenyl or phenylene.
In the context of the present invention, the heteroaryl radical indicated as Het signifies preferably a 5- to 7-membered, aromatic or non-aromatic ring with one to three hetero atoms selected from the group comprising N, O and S. Preference is given to aromatic 5- and 6-rings, which have a nitrogen atom as the hetero atom and optionally one further hetero atom, preferably nitrogen, oxygen or sulphur, especially nitrogen.
It has now surprisingly been found that the method according to the invention is able to satisfy the requirements mentioned initially.
The hydrolysis process according to the invention may be carried out both in an acidic and in a basic medium. In the acidic range, pH values of 6 or less, especially 1 to 3, are preferred. In the basic range, a pH value greater than 7 and up to 12, especially 8 to 12, in particular 8 to 10, is preferred. The reaction is carried out at normal pressure and at a temperature of 0 to 120xc2x0 C., preferably 20 to 80xc2x0 C.
The reaction is carried out in a solvent or diluent that is inert towards the reaction components. Suitable solvents are, in particular, alcohols such as methanol, ethanol, propanol and isopropanol, as well as especially water. Further appropriate solvents are e.g. ethers, such as tetrahydrofuran and dioxane, as well as other solvents which do not adversely affect the reaction. The solvents may also be used as mixtures. A compound of formula (II) is preferably hydrolysed in an aqueous medium or in a mixture of water with an alcohol.
Suitable acids for carrying out the process are preferably mineral acids, e.g. sulfuric acid, a phosphoric acid or a hydrohalic acid, an organic carboxylic acid, typically C1-C4alkanecarboxylic acids substituted where appropriate for example by halogen, e.g. acetic acid, such as dicarboxylic acids that are unsaturated where necessary, e.g. oxalic, malonic, maleic, fumaric or phthalic acid, typically hydroxycarboxylic acids, e.g. ascorbic, lactic, malic, tartaric or citric acid, or benzoic acid, or an organic sulfonic acid, typically C1-C4alkane- or arylsulfonic acids substituted where appropriate for example by halogen, e.g. methanesulfonic or p-toluenesulfonic acid.
Suitable bases for carrying out the process are preferably hydroxides of alkali metals and alkaline earth metals, such as NaOH and KOH, carbonates such as Na2CO3, NaHCO3, K2CO3; phosphates such as Na3PO4, Na2HPO4, alcoholates such as sodium methaholate, sodium ethanolate and K-tert.-butanolate, organic amines such as morpholine, piperidine, pyrrolidine, a mono-, di- or tri-lower alkylamine, e.g. ethyl-, diethyl, triethyl- or dimethylpropyl-amine, or a mono-, di- or trihydroxy lower alkylamine, e.g. mono-, di- or triethanolamine, or dialkylaniline, for example N,N-dimethyl- or N,N-diethylaniline, as well as salts of organic acids, such as sodium acetate, potassium acetate or sodium benzoate, or mixtures thereof, for example acetate or phosphate buffers.
Especially advantageous reaction conditions are described in the examples.
The method according to the invention is preferably used to produce compounds of formula (I) in which the heterocyclic radical Het is unsaturated and is bonded by a carbon atom as a ring member to the fundamental substance. Especially preferred radicals Het are pyridyl, thiazolyl, tetrahydrofuranyl, dihydrofuranyl, furanyl, N-oxido-pyridinio, oxazolyl, isoxazolyl, thienyl, morpholinyl, piperidinyl, pyridinyl and pyrazinyl; particularly pyridyl, thiazolyl, tetrahydrofuranyl and N-oxido-pyridinio, most particularly 3-pyridyl, 2-halogenpyrid-5-yl, 2,3-dihalogenpyrid-5-yl, 2-halogenthiazol-5-yl, tetrahydrofuran-3-yl, 2-methyl-tetrahydrofuran-4-yl, 1-oxopyrid-3-yl, 1-oxo-2-halogenpyrid-5-yl and 1-oxo-2,3-dihalogenpyrid-5-yl.
Equally preferably, the heterocycles Het carry one to three substituents from the group halogen, C1-C3-alkyl, C1-C3-halogenalkyl and C1-C3-halogenalkoxy each with 1 to 7 halogen atoms, and C1-C3-alkoxy, most preferably chlorine or methyl.
Furthermore, compounds of formula (I) are preferably produced according to the invention, in which the radical B is a phenyl, pyridyl or thiazolyl radical that is unsubstituted or may be substituted by one to two radicals from the group halogen, C1-C3-alkyl, C1-C3-halogenalkyl and C1-C3-halogenalkoxy each with 1 to 7 halogen atoms, and C1-C3-alkoxy.
Of the compounds of formula (I) to be produced according to the invention, the notable ones are those in which
R1 is hydrogen;
R2 is hydrogen, C1-C3-alkyl or cyclopropyl; especially hydrogen, methyl, ethyl or cyclopropyl, in particular methyl; and
Het is pyridyl, 1-oxopyridyl, tetrahydrofuranyl, thiazolyl; or pyridyl, 1-oxidopyridinio, tetrahydrofuranyl or thiazolyl, respectively substituted by one to three substituents from the group halogen, C1-C3-alkyl, C1-C3-halogenalkyl as well as C1-C3-halogenalkoxy with 1 to 7 halogen atoms and C1-C3-alkoxy;
xe2x80x83especially 2-chloropyrid-5-yl, tetrahydrofuran-3-yl, 2-methyl-tetrahydrofuran4-yl or 2-chloro-thiazol-5-yl.
To carry out the process according to the invention, on the one hand preferably those compounds of formula (IIa) are used, in which A is straight-chained or branched C2-C20-alkylene, C2-C20-alkenylene, C2-C20-alkynylene, C3-C12-cycloalkylene, arylene or heterocyclylene; whereby the groups C2-C20-alkylene, C2-C20-alkenylene, C2-C20-alkynylene, C3-C12-cycloalkylene, arylene and heterocyclylene are optionally substituted once or several times, independently of each other, and the groups C2-C20-alkylene, C2-C20-alkenylene and C2-C20-alkynylene are optionally interrupted once or several times, independently of each other, by O, Nxe2x80x94H or Nxe2x80x94C1-C12-alkyl, C3-C9-cycloalkylene, arylene or heterocyclylene; or a group xe2x80x94D1xe2x80x94D2xe2x80x94D3xe2x80x94; wherein
D1 and D3, independently of each other, signify optionally substituted C3-C12-cycloalkylene or arylene and D2 signifies C2-C20-alkylene, C2-C20-alkenylene, C2-C20-alkynylene, O, Nxe2x80x94H or Nxe2x80x94C1-C12-alkyl.
Particularly preferred bridging members A are C2-C12-alkylene, C2-C12-alkylene interrupted by one or two phenylene, cyclohexylene or piperazinylene radicals; cyclohexylene or phenylene; or the group xe2x80x94D1xe2x80x94D2xe2x80x94D3xe2x80x94, wherein D1 and D3 are phenylene or dicyclohexylene and D2 is O or C2-C4-alkylene; A especially signifies C2-C4-alkylene.
On the other hand, in order to carry out the process according to the invention, preferably compounds of formula (IIb) are used as the starting material, wherein U is aryl, heterocyclyl, C3-C12-cycloalkyl or a group 
wherein
A1, A2 and A3 independently of one another, have the same significances as given above for A in formula (IIa), and
X signifies N or CH.
Heterocyclyl A and U in the compounds of formulae (IIa) and (IIb) is preferably an aromatic or non-aromatic, three- to ten-membered ring. If the rings A and U are aromatic, they are preferably the same rings as defined above for Het. If the rings A and U are non-aromatic heterocyclic rings, they are especially piperidinyl, piperazinyl, morpholinyl, pyrrolidinyl, tetrahydrofuranyl and dioxolanyl. The radicals A1, A2 and A3 independently of one another are most preferably C2-C4-alkylene, especially ethylene.
A further object of the invention is
b) a method of producing a compound of formula (IIa) and (IIb), in which a compound of formula
Txe2x80x94Axe2x80x94Txe2x80x83xe2x80x83(IIIa),
xe2x80x83or of formula 
wherein A and U have the same significance as defined above for formulae (IIa) and (IIb); 
and R2 has the same significance as defined above for formula (I);
and optionally the E/Z isomers, E/Z isomeric mixtures and/or tautomers thereof, each in free form or in salt form, is reacted when producing a compound of formula (IIIa) with two equivalents or when producing a compound of formula (IIIb) with three equivalents of a compound of formula 
which is known or may be produced analogously to methods known per se, wherein R1 and Het are defined as given above for formula (I) and Y is a leaving group, preferably in the presence of a base.
The following may be considered as the leaving group Y in the context of the described method of operation: halogen, preferably chlorine, bromine or iodine, especially chlorine, or sulfonic acid radicals, such as alkylsulfonic acid radicals, mesylate or tosylate.
The process step according to b) may be carried out preferably at normal or at a slightly raised pressure and in the presence of preferably aprotic solvents or diluents. Suitable solvents or diluents are e.g. ethers and ether-type compounds, such as diethyl ether, dipropyl ether, dibutyl ether, dioxane, dimethoxyethane and tetrahydrofuran; aliphatic, aromatic and halogenated hydrocarbons, especially benzene, toluene, xylene, chloroform, methylene chloride, carbon tetrachloride and chlorobenzene; nitriles such as acetonitrile or propionitrile; dimethyl sulfoxide or dimethyl formamide, as well as mixtures of these solvents. This process step is generally carried out at a temperature of xe2x88x9220xc2x0 C. to +140xc2x0 C., preferably between 0xc2x0 C. and +120xc2x0 C., preferably in the presence of a base. Suitable bases are e.g. carbonates, such as sodium and potassium carbonate. Hydrides may also be used as bases, for example sodium hydride, potassium hydride and calcium hydride. If required, the reaction can also be carried out in the presence of a catalyst, e.g. cesium chloride.
A further object of the invention is
c) a method of producing the compounds of formula (IIa) and (IIIb), in which a compound of formula
H2Nxe2x80x94Axe2x80x94NH2xe2x80x83xe2x80x83(Va),
xe2x80x83or 
and optionally the E/Z isomers, E/Z isomeric mixtures and/or tautomers thereof, each in free form or in salt form, wherein A and U have the same significance as defined above for the compounds of formulae (IIa) and (IIb), and which are known or may be produced analogously to methods known per se, is reacted when producing a compound of formula (IIIa) either with two equivalents, or when producing a compound of formula (IIIb) with three equivalents of a compound of formula 
which is known or may be produced analogously to methods known per se, and wherein R2 has the same significance as defined for formula (I), in the presence of an excess of formaldehyde or paraformaldehyde.
The process according to c) for the preparation of the compounds of formula (III) is advantageously carried out at normal pressure, but also optionally at a raised pressure in the presence of an inert solvent and at temperatures of between 0C and +140xc2x0 C., preferably between +20xc2x0 C. and +120xc2x0 C. Suitable solvents are, in particular, alcohols such as methanol, ethanol, and propanol, as well as water. Further suitable solvents are e.g. aromatic hydrocarbons, such as benzene, toluene and xylene; ethers such as tetrahydrofuran, dioxane and diethyl ether, halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride and chlorobenzene, as well as other solvents which to not impair the reaction. The solvents may also be used as mixtures. The process is optionally effected adding an acidic catalyst, such as HCl, H2SO4 or a sulfonic acid, such as p-toluene-sulfonic acid. The resulting reaction water may be removed, if desired, using a water separator or by adding a molecular sieve.
A further object of the invention is
d) a method of producing a compound of formula (I), in which a compound of formula (Va) or (Vb) is converted into a compound of formula (IIIa) or (IIIb) by reacting it with a compound of formula (VI) and formaldehyde or paraformaldehyde; this compound of formula (IIIa) or (IIIb) is converted by a compound of formula (IV) into a compound of formula (IIa) or (IIb) and this compound of formula (IIa) or (IIb) is hydrolysed.
Further objects of the invention are the compounds of formulae (IIa), (IIb), (IIIa) and (IIIb), and optionally the E/Z isomers, E/Z isomeric mixtures and/or tautomers thereof, each in free form or in salt form, as well as the use thereof in the preparation of compounds of formula (I).